1. Field of the Invention
Embodiments of the invention are in the field of gear structures and, more particularly, pertain to bidirectional gear structures and gear structure pairs (sets), a method for making, and applications thereof.
2. Related Art
Gears are used extensively in engineering. Numerous different gear designs exist that are specialized for the individual needs of various applications. A non-limiting sample of the different existing gears includes: spur gears, rack and pinion gears, internal ring gears, helical gears, helical rack gears, face gears, worm gears, double enveloping worm gears, hypoid gears, straight bevel gears, spiral bevel gears, and screw gears. All of these gears are capable of transmitting motion or power in one direction. Gears can be designed to have the output gear shaft perpendicular to the input gear shaft, like bevel gears, with which the power transmission direction can be changed by 90 degrees. However, there is still only one power and motion transmission direction with a pair of gears. To achieve motion in two different directions more than two gears are typically needed.
Bullard U.S. Pat. No. 2,453,656 discloses rack and pinion gear means comprising an arrangement of positive acting, intermeshing means for transmitting oscillatory and reciprocatory motions between two angularly-related shafts. More particularly, with reference to FIG. 1, a toothed member A is keyed to a shaft 10, which can be reciprocated along and oscillated about its longitudinal axis. A similar toothed member B is keyed to a shaft 11 at substantially right angles to shaft 10, which shaft 11 can also be oscillated about and reciprocated along its longitudinal axis. Each of the members A and B comprises relatively long bodies 12 having elongated spur gear teeth 13 formed about their peripheries. Equally-spaced circumferential grooves 14 are cut in the teeth 13 to a depth of or slightly below, the pitch circle of the spur teeth 13. These grooves 14 are machined such that the walls 15 formed by them conform to addendum surface 16 of the spur teeth 13. The grooves 14, therefore, provide axially-aligned teeth having dedendum height only, which alternate with teeth in the same axial row having both addendum and dedendum height. Additionally, these grooves form circumferential rows of teeth having dedendum height only, which rows alternate with circumferential rows of teeth having both addendum and dedendum height.
A developing application of bi-directional gears is robots. For example, structure-climbing robots have traditionally been developed to perform tasks currently carried out by humans, ranging from structural inspections to cleaning and maintenance. One object of the inventors' work is to explore both robot and structure design to expand the range of tasks that can be successfully completed autonomously. For example, a robot capable of modifying a structure by taking it apart and rebuilding it into a different shape would be advantageous. Such ‘structure-reconfiguring’ robots could have a profound impact on construction processes, especially activities involving frame construction. Furthermore, the ability to autonomously repair a damaged structure or autonomously adapt an existing structure to a new function can have applications ranging from disaster recovery to space exploration.
One of the key challenges in designing a structure-reconfiguring robot is that most current structural building blocks are designed for manipulation by humans, not by machines. Structural joints require complex assembly, and truss elements are cumbersome to manipulate. The development of standards for joint connections and elements has been crucial in the progress of modular assembly in the construction industry. Furthermore, the lack of robot-friendly joints and elements has significantly limited the deployment of robots in the construction field. It would be particularly advantageous to have a structure-reconfiguring robot that could maneuver between the horizontal and vertical planes of a structure and traverse multiple nodes in one run. Bi-directional gear drives may make this capability a possibility. The gear means described in Bullard '656 (referred to above) do not provide this capability because the similar crossed gear shafts cannot prevent their relative sliding when they are in a parallel orientation, but only when they are in a perpendicular orientation.
The inventors have recognized a need for, and the benefits of, a solution to, e.g., the problems faced in the successful development of structure-reconfiguring robots, which solutions the aforementioned art do not provide.